WO2006/001759A1 issued to the assignee of the present invention, discloses a method and means for detection of blood leakage from wounds by means of an optical fiber. The optical fiber is arranged in a loop from a light source to a patch to be attached to the patient and back to a light detector. The light source and light detector are arranged in a monitoring device at a distance from the patch and may be attached to the arm of a patient. The loop comprises a sensor portion arranged at the patch and in which the optical fiber is bent with a small radius, so that the total internal reflection angle inside the optical fiber is approached or exceeded. A portion of the light transmitted through the optical fiber passes out through the sidewall of the optical fiber in the small radius sensor portion. When the sensor portion is exposed to a fluid, such as water or blood, the portion of the light passing out through the sidewall of the optical fiber in the small radius sensor portion increases, which may be sensed by the light detector as a decrease in light intensity, which may trigger an alarm.
The device according to WO2006/001759A1 operates well and is able to monitor for example a vascular access in an extracorporeal treatment, such as dialysis.
However, the manufacturing costs of said device may be further decreased. In addition, the amount of surplus material during manufacturing may be reduced. Furthermore, the security of the connection of the patient device to the monitor may be improved. However, a reduction of costs and operation requires a new technology to be used.
It is noted that the patient portion should be sterile and is disposable. However, the monitoring unit including the light source and detector and further electronic circuits is reusable. Thus, a reduction of costs per treatment may be obtained by reducing the costs of the disposable patient portion.
Another problem is relocation of the patch when the optical fiber is exposed to a force. When the patient is moving, the optical fiber may be influenced upon resulting in the fact that the patch is removed. This may remain unnoticed for a long time. When it is noticed, it is sometimes difficult to relocate the patch and it may be required to attach a new patch. If the relocation remains unnoticed, this is a safety risk.